Last December, Jon Corzine appeared before a congressional committee investigating the spectacular collapse of MF Global, the financial broker that had gone bankrupt five weeks earlier, leaving $1.6 billion in client funds missing. In his testimony, Corzine, MF Global’s CEO at the time of the collapse, said, “I simply do not know where the money is.” But a newly disclosed Congressional memo appears to contradict Corzine’s testimony, raising questions about whether he lied to Congress.

The Department of Justice and the Securities and Exchange Commission are investigating whether MF Global illegally used client funds to cover company losses. Federal securities law requires brokers like MF Global to keep client money and firm money separate — in order to protect customers if the firm fails, as MF Global did. Investigators now estimate that $1.6 billion worth of client money remains missing, including $100 million worth of commodity contracts owed to ranchers and farmers.

While not a smoking gun, the memo details an email from an assistant treasurer at MF Global saying that $200 million was transferred from a customer account to cover an overdraft elsewhere at the firm, “Per JC’s [Jon Corzine’s] direct instructions.” It was released ahead of a hearing on MF Global’s collapse set for this Wednesday by the Financial Services Subcommittee on Oversight and Investigations. “We hope to learn whether the liquidity crunch at MF Global led someone to improperly use customer funds to meet the firm’s need for cash,” Financial Services Committee Chairman Spencer Bachus said in a statement.

After taking over as MF Global’s CEO in March of 2010, Corzine, a former Democratic New Jersey senator and governor, embarked on an ambitious course to turn the firm into a financial powerhouse. Corzine had famously been pushed out as CEO of Goldman Sachs in the 1990s and he still had something to prove on Wall Street, according to a recent Vanity Fair story. “It seemed as if he was trying to build a mini Goldman Sachs,” according to the article, by Bryan Burrough, William D. Cohan and Bethany McLean.

As part of that effort, Corzine personally engineered huge bets on European sovereign debt — wagers that went bad as the European debt crisis intensified in the fall of 2011. In the days leading up to MF Global’s bankruptcy filing, on October 31, 2011, the firm struggled frantically to cover its losses.

On October 28, 2011, according to a memo released Friday by the subcommittee, Corzine personally ordered $200 million to be transferred from a customer account to cover a $175 million overdraft at another of the firm’s accounts, at the London office of JPMorgan Chase. The memo refers to an email from Edith O’Brien, an assistant treasurer at MF Global, which says that the transfer was made, “Per JC’s [Jon Corzine’s] direct instructions.”

The O’Brien email raises two important issues.

The first is whether Corzine ordered so-called “segregated” — or safe — client funds to be transferred to company accounts in order to cover losses incurred by the firm, which would be a serious violation of securities law. On this question, the O’Brien email is not — in itself — a smoking gun. That’s because while the account in question was a customer account, it could have also contained company funds, according to the Congressional memo, which notes that futures brokers like MF Global are permitted to deposit company funds in customer accounts “in excess of segregation requirements,” which “may be transferred out of the segregated accounts.”

Throughout the course of its chaotic final week, as its financial condition worsened, MF Global “represented to its regulators and self-regulatory organizations that its customers’ segregated funds were safe,” according to the memo. But after the transfer, according to the memo, JPMorgan was concerned enough about the source of the funds to send MF Global a letter to be signed by O’Brien that would give “broad assurances that all transfers — past, present and future” complied with federal rules prohibiting customer funds from being used to cover company losses.

According to the memo, the letter was never returned to JPMorgan, and a series of emails show that O’Brien was reluctant to sign it.

The second question raised by the memo is more prosaic: Did Corzine lie to Congress? In his December testimony, Corzine said of the missing customer money: “I simply do not know where the money is, or why the accounts have not been reconciled to date.” On this question, the memo doesn’t appear to provide a smoking gun either. That’s because although Corzine personally ordered $200 million to be transferred from an account that contained customer funds to the JPMorgan account, according to O’Brien, it’s not clear that the transferred funds actually were customer funds.

For his part, Corzine is sticking to his story. “He stands by that testimony,” Corzine spokesperson Steven Goldberg said in statement after the memo was released. “He never directed Ms. O’Brien or anyone else regarding which account should be used to cure the overdrafts, and he never directed that customer funds should be used for that purpose. Nor was he informed that customer funds had been used for that purpose.”

Although the memo does not contain definitive evidence that Corzine ordered customer funds to be used to cover company losses — or knew that was occurring — his zone of plausible deniability appears to be shrinking. All eyes will be on the congressional hearing on Wednesday when several of Corzine’s former MF Global colleagues, including O’Brien, testify about the final days of the firm. But further details from O’Brien may not be forthcoming. According to The New York Times, she plans to invoke her Fifth Amendment right against self-incrimination.

Update 3/26 11 a.m. EST: The New York Times is reporting the existence of another email sent to Corzine on Oct. 28 that said the transfer to JPMorgan was a “House Wire,” meaning it came from the firm’s funds in a “nonseg” (noncustomer) account. The email bolsters Corzine’s contention that he was not aware of any customer money being used to cover company losses. Additionally, Corzine’s spokesperson, Steven Goldberg, has issued a further statement:

As Mr. Corzine testified before Congress, he asked that the overdrafts with JP Morgan be corrected. As he also testified, he never gave any instruction to misuse customer funds and never intended anyone at MF Global to misuse customer funds. He further testified that he didn’t believe anything he said could reasonably have been interpreted as an instruction to misuse customer funds. He stands by that testimony. He never directed Ms. O’Brien or anyone else regarding which account should be used to cure the overdrafts, and he never directed that customer funds should be used for that purpose. Nor was he informed that customer funds had been used for that purpose. To the contrary, as Mr. Corzine testified, he recalls having received written material indicating that the funds used to cure the overdrafts were appropriate for that purpose. As Mr. Corzine testified, it was his understanding that on the evening of October 27th, MF Global had substantial hundreds of millions of dollars in cash and free collateral available.